雨水入渗下非饱和黏性土路基边坡浅层稳定分析

Shallow Stability Analysis for Unsaturated Clay Slope of Subgrade under Rainwater Infiltration

为合理评估雨水作用下非饱和土黏性土路基边坡浅层稳定性,针对单位土条式“无限长斜坡法”,力学上忽略滑体上下缘抗滑效应的缺陷,提出降雨诱发的黏性土路基边坡浅层滑动,由滑体上缘张拉区和下缘挤压区为异心圆弧面,中段主滑区为顺坡平面的异心式“顺坡曲面”失稳模式,推导了“顺坡曲面”组合滑面几何方程和滑体静力平衡方程,基于双应力状态变量的非饱和土抗剪强度模型,建立了雨水入渗下反映顺坡面上水位抬升影响的非饱和黏性土路基边坡浅层稳定分析方法。分析表明:非饱和入渗黏性土路基边坡,前期以雨水浸润下土体吸附强度大幅衰减,安全系数线性降低为主;后期以雨水下渗抵达不(弱)透水层形成薄层积水,引起安全系数突变为特征,加剧了边坡失稳破坏的可能性;研究成果可为考虑降雨特性的路基边坡稳定性研究提供参考。

In order to evaluate the shallow stability of unsaturated clay slope induced by rainfall,the defects of the infinite slope method based on the"parallel slope-plane"failure mode ignoring the anti-sliding effect of the upper and lower edges of the sliding body were analyzed.The shallow failure mode of composite"parallel slope-curve"including a upper tension zone and a lower squeeze zone for arc surface of different center,and a main sliding zone in the middle was presented.The geometric equations of composite surface and sliding equilibrium equations of slide body were also deduced.In accordance with the shear strength model of dual stress state variables for unsaturated soils,an analysis method of shallow stability for unsaturated clay slope under rainwater infiltration was established,which can reflect the effect of rising water level on the inner parallel slope surface.The results show that the safety factor decreases linearly with the decrease of the adsorption strength of the soil in the early stage of rainwater infiltration into the unsaturated clay slope.In the later stage,the rainwater infiltrates into the impervious or weak permeable layer to form a thin layer of water,which causes a sudden change in the safety factor,and intensifies the possibility of slope instability.The research can provide reference for the study of subgrade slope stability considering rainfall characteristics.